The present invention relates to a plasma processing method such as dry etching, sputtering, and plasma CVD, as well as apparatus therefor, to be used for manufacture of semiconductor or other electron devices and micromachines. More particularly, the present invention relates to plasma processing method and apparatus for use of plasma excited with high-frequency power of VHF or UHF band.
Whereas Japanese Unexamined Patent Publication No. 8-83696 describes that use of high-density plasma is important in order to meet the trend toward microstructures of semiconductors and other electron devices, low electron temperature plasma has recently been receiving attention by virtue of its high electron density and low electron temperature.
In the case where a gas having a high negativity, i.e., a gas that tends to generate negative ions, such as Cl2 and SF6, is formed into plasma, when the electron temperature becomes about 3 eV or lower, larger amounts of negative ions are generated than with higher electron temperatures. Taking advantage of this phenomenon makes it possible to prevent etching configuration abnormalities, so-called notch, which may occur when positive charges are accumulated at the bottom of micro-patterns due to excessive incidence of positive ions. This allows etching of extremely micro-patterns to be achieved with high precision.
Also, in the case where a gas containing carbon and fluorine, such as CxFy or CxHyFz (where x, y, z are natural numbers), which is generally used for etching of insulating films such as silicon oxide, is formed into plasma, when the electron temperature becomes about 3 eV or lower, gas dissociation is suppressed more than with higher electron temperatures, where, in particular, generation of F atoms, F radicals and the like is suppressed. Because F atoms, F radicals, and the like are higher in the rate of silicon etching, insulating film etching can be carried out at larger selection ratios to silicon etching the more with lower electron temperatures.
Also, when the electron temperature becomes 3 eV or lower, ion temperature and plasma potential also lower, so that ion damage to the substrate in plasma CVD can be reduced.
It is plasma sources using high-frequency power of VHF or UHF band that are now receiving attention as a technique capable of generating plasma having low electron temperature.
FIG. 9 is a sectional view of a plate antenna type plasma processing apparatus we have already purposed. Referring to FIG. 9, while interior of a vacuum chamber 101 is maintained to a specified pressure by introducing a specified gas from a gas supply device 102 into the vacuum chamber 101 and simultaneously performing exhaustion by a pump 103 as an exhausting device, a high-frequency power of 100 MHz is supplied by an antenna use high-frequency power supply 104 to an antenna 105 via a through hole 107 provided in a dielectric plate 106 which is sandwiched between the antenna 105 and the vacuum chamber 101 and which is generally equal in outer dimensions to the antenna 105. Then, plasma is generated in the vacuum chamber 101, where plasma processing such as etching, deposition, and surface reforming can be carried out on a substrate 109 placed on a substrate electrode 108. In this process, as shown in FIG. 9, by supplying high-frequency power also to the substrate electrode 108 by a substrate-electrode use high-frequency power supply 110, ion energy that reaches the substrate 109 can be controlled. In addition, the surface of the antenna 105 is covered with an insulating cover 111.
Also, a plasma trap 114 formed of a recessed space between the antenna 105 and a conductor ring 113 provided around the antenna 105 is provided. With such a constitution, because electromagnetic waves radiated from the antenna 105 are intensified by the plasma trap 114, and because hollow cathode discharge is liable to occur in plasma at low electron temperatures, it becomes easier to generate high-density plasma (hollow cathode discharge) with the plasma trap 114 surrounded by solid surfaces. Therefore, within the vacuum chamber 101, plasma density becomes the highest at the plasma trap 114, and plasma is transported up to near the substrate 109 by diffusion, by which more uniform plasma can be obtained.
However, there has been an issue that the conventional method shown in FIG. 9 has difficulty in ignitability (start of discharge) at low pressure. It was found that with chlorine gas supplied into the vacuum chamber 101, and with a VHF power of 1000 W applied to the antenna 105, ignition could not be obtained at 0.3 Pa or lower pressures. Also, with the conventional method shown in FIG. 9, ion saturation current density in the vicinity of the substrate 109 is so low that with chlorine gas supplied into the vacuum chamber 110, and with a VHF power of 1000 W applied to the antenna 105, the result was 1.41 mA/cm2 for 1 Pa.
In view of these issues of the prior art, an object of the present invention is to provide plasma processing method and apparatus superior in ignitability and capable of obtaining high ion saturation current density.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is generally equal in outer dimensions to the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber and, simultaneously therewith, exhausting the interior of the vacuum chamber, thus generating plasma; and
processing the substrate while plasma distribution on the substrate is controlled by a plasma trap made up of a groove-shaped space between the dielectric plate and a dielectric ring provided around the dielectric plate, and a groove-shaped space between the antenna and a conductor ring provided around the antenna.
According to a second aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is larger in outer dimensions than the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber and, simultaneously therewith, exhausting the interior of the vacuum chamber, thus generating plasma; and
processing the substrate while plasma distribution on the substrate is controlled by a plasma trap formed of a groove-shaped space between the antenna and a conductor ring provided around the antenna.
According to a third aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is larger in outer dimensions than the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber and, simultaneously therewith, exhausting the interior of the vacuum chamber, thus generating plasma; and
processing the substrate while plasma distribution on the substrate is controlled by a plasma trap made up of a groove-shaped space between the antenna and a conductor ring provided around the antenna and a groove-shaped space between the dielectric plate and the conductor ring.
According to a fourth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed while a short pin short-circuits the antenna and the vacuum chamber to each other so as to give an isotropic electromagnetic field distribution to the antenna.
According to a fifth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed while a surface of the antenna is covered with an insulating cover.
According to a sixth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed while the dielectric plate is made up of a plurality of dielectric plates different in material from each other or one another.
According to a seventh aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the substrate is processed while no DC magnetic fields are present within the vacuum chamber.
According to an eighth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply device for supplying gas into the vacuum chamber;
an exhausting device for exhausting interior of the vacuum chamber;
a substrate electrode for placing thereon a substrate within the vacuum chamber;
an antenna provided opposite to the substrate electrode;
a dielectric plate sandwiched between the antenna and the vacuum chamber and being generally equal in outer dimensions to the antenna; and
high-frequency power supply for supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to the antenna via a through hole provided in the dielectric plate,
wherein a plasma trap made up of a groove-shaped space between the dielectric plate and a dielectric ring provided around the dielectric plate, and a groove-shaped space between the antenna and a conductor ring provided around the antenna, is provided.
According to a ninth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply device for supplying gas into the vacuum chamber;
an exhausting device for exhausting interior of the vacuum chamber;
a substrate electrode for placing thereon a substrate within the vacuum chamber;
an antenna provided opposite to the substrate electrode;
a dielectric plate sandwiched between the antenna and the vacuum chamber and being larger in outer dimensions than the antenna; and
high-frequency power supply for supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to the antenna via a through hole provided in the dielectric plate,
wherein a plasma trap formed of a groove-shaped space between the antenna and a conductor ring provided around the antenna, is provided.
According to a tenth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply device for supplying gas into the vacuum chamber;
an exhausting device for exhausting interior of the vacuum chamber;
a substrate electrode for placing thereon a substrate within the vacuum chamber;
an antenna provided opposite to the substrate electrode;
a dielectric plate sandwiched between the antenna and the vacuum chamber and being larger in outer dimensions than the antenna; and
high-frequency power supply for supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to the antenna via a through hole provided in the dielectric plate,
wherein a plasma trap made up of a groove-shaped space between the antenna and a conductor ring provided around the antenna and a groove-shaped space between the dielectric plate and the conductor ring, is provided.
According to an 11th aspect of the present invention, there is provided a plasma processing apparatus according to the eighth aspect, further comprising a short pin for short-circuiting the antenna and the vacuum chamber to each other.
According to a 12th aspect of the present invention, there is provided a plasma processing apparatus according to the eighth aspect, wherein a surface of the antenna is covered with an insulating cover.
According to a 13th aspect of the present invention, there is provided a plasma processing apparatus according to the eighth aspect, wherein the dielectric plate is made up of a plurality of dielectric plates different in material from each other or one another.
According to a 14th aspect of the present invention, there is provided a plasma processing apparatus according to the eighth aspect, wherein the vacuum chamber is equipped inside with no coil or permanent magnet for applying a DC magnetic field into the vacuum chamber.
According to a 15th aspect of the present invention, there is provided a plasma processing apparatus according to the eighth aspect, wherein a diameter of the antenna is 50-90% of a diameter of the substrate.